The present invention relates to a laminated magnetic head core for use in VTR or the like system driven in the high frequency band region.
As it has been increasingly required to record data with high density in the field of magnetic recording, a magnetic recording medium is designed to show higher coercive force. For this purpose, a magnetic head core is necessary to have the high saturation magnetic flux density (mainly influencing the recording characteristic of the magnetic head) and high magnetic permeability (mainly influencing the playback or reproducing characteristic of the magnetic head). At the same time, since the carrier frequency becomes higher, good recording/reproducing performance in the high frequency band, namely, not lower than several tens MHz is needed for the magnetic head. However, a conventional ferrite head cannot meet these requirements because the saturation magnetic flux density is small, and the ferrite head is magnetically saturated to a medium with high coercive force, resulting in poor recording quality. Such being the circumstances, Sendust (Fe--Al--Si system) or cobalt base amorphous alloy is now actually used for the magnetic head.
Sendust or cobalt base amorphous alloy has the saturation magnetic flux density so small as approximately 1 T and cannot record well to a magnetic recording medium with high coercive force. Therefore, a microcrystal and soft magnetic film, e.g., Fe--(Ta,Zr,Nb,Hf)--(B,C,N) is catching attention lately.
Meanwhile, there are roughly two kinds of magnetic heads using an alloy film, one is a MIG head equipped with an alloy film only in the vicinity of the gap of the ferrite head and the other is a laminated head wherein alloy films are laminated on a non-magnetic substrate via non-magnetic insulating films.
The above-referred MIG head and laminated head using alloy films in the prior art will be depicted below.
FIG. 5 indicates the constitution of a conventional MIG head, in which 21 shows ferrite, 22 is a gap, 23 is a magnetic film formed of Sendust alloy or cobalt base amorphous alloy, etc. in the vicinity of the gap 22, and 24 represents glass.
In the constitution in FIG. 5, since ferrite which shows relatively good magnetic permeability in several MHz and an alloy film showing higher saturation magnetic flux density than ferrite are combined, the performance required for the magnetic head is improved.
FIG. 6 illustrates a conventional laminated head. In FIG. 6, 31 and 32 are a non-magnetic substrate and a gap, respectively. A magnetic film 33 is obtained by alternately laminating several .mu.m Sendust alloy films or cobalt base amorphous alloy films and non-magnetic insulating films. Reference numeral 34 denotes glass.
In the structure of FIG. 6 without using ferrite, slide noises peculiar to ferrite are not generated, so that the performance of the head is improved.
The MIG head as above is not free from slide noises specific to ferrite, and invites more slide noises particularly in the high frequency band. The playback characteristic in the high frequency band is consequently deteriorated. In contrast, when the laminated head which has Sendust alloy films or cobalt base amorphous alloy films alternately laminated over the non-magnetic insulating films is used, slide noises can be eliminated, but the soft magnetic characteristic is degraded if each magnetic layer is reduced to approximately 3 .mu.m thickness or smaller as disclosed in Japanese Patent Publication No. 54-3238 (3238/1979). That is, it is impossible to reduce the thickness of each magnetic layer to not larger than 3 .mu.m or so. Therefore, the eddy current core loss cannot be satisfactorily restricted and the isotropic high magnetic permeability cannot be secured although it is an important factor for the laminated head to be used in VTR, etc. driven in the high frequency band.
If an Fe--(Ta,Nb,Zr,Hf)--N system soft magnetic thin film with high saturation magnetic flux density is made thinner so as to improve the high frequency characteristic, specifically, not larger than 1 .mu.m, although the high magnetic permeability is obtained in a direction difficult to magnetize by inducing the uniaxial anisotropy through a thermal treatment in the static magnetic field, etc., the desired isotropic high magnetic permeability is not achieved.